Lesson 6: Practical Guidelines for OCPD Ampere Rating Sizing /
Quiz yourself by thinking what should be in
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| show | d. All of the above
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| In some cases, momentary high inrush currents during motor starting can reach as high as ? times the normal running current amperes during the first 1/2 cycle. Select one: a. 2 b. 4 c. 10 d. 20 | show 🗑
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| show | True
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| show | Tue
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| Which of the following is typically true regarding motor overcurrent protection? I. Motor branch-circuit short-circuit and ground-fault protection is located at the beginning of a motor branch circuit in order to provide short-circuit and ground-fault | show 🗑
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| Which NEC section provides the separate overload device rating or trip setting requirement for continuous-duty motors more than one horsepower? | show 🗑
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| A motor with a service factor number is designed to operate above its _____________ rating | show 🗑
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| 9.Separate motor and branch-circuit overload protection is sized based upon the ? a. Full load current based on motor horsepower in NEC Tables 430.247 to 430.250 b. maximum locked-rotor current c. motor nameplate full-load current d. start-up curr | show 🗑
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| show | c. 40 A
Note: 32 × 1.25 = 40 A. See 430.32(A)(1).
The correct answer is: 40 A
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| 11. Using the conductor sizing guide in this lesson, what conductor ampacity is needed for a 10-horsepower, 230-volt single phase motor? | show 🗑
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| show | b. 115%
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| 13.According to 430.32, if a continuous-duty motor nameplate does not have a 1.15 or greater service factor or temperature rise of 40°C or less, then a separate overload protection device must be set at no more than ? (assuming that this selection wil | show 🗑
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| 14.Using 430.52 and Table 430.248, what is the maximum size dual-element fuse short-circuit and ground-fault protective device allowed for a 10-horsepower, 230-volt, single-phase motor, assuming the motor starts with this size? a. 50 A b. 70 A c. 8 | show 🗑
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| show | 272 A
Note: 34 × 800% = 272 A
The circuit breaker in this question is an instantaneous trip only circuit breaker which does not have an overload sensing element. Do not confuse this with a thermal magnetic circuit breaker. This result is the setting of
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| 16. Instantaneous trip circuit breakers are also referred to as motor circuit protectors (MCPs) and are intended only for motor branch circuit short-circuit and ground-fault protection. True False | show 🗑
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| 17.Overcurrent protection for transformers requires special considerations due to the magnetizing inrush current, which occurs on the ? when the transformer is energized. a.primary Correct b. secondary c. primary and secondary | show 🗑
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| 18.Size the maximum primary and secondary overcurrent devices for a 100-kilovolt-amperes, 3-phase transformer, a 480-volt primary, and a 208/120 volts secondary (Only consider the transformer and not conductor protection or panelboard protection). a. | show 🗑
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| 19.The purpose of overcurrent protection of capacitors is for ? a. delay sequence protection b. ground-fault protection c. overload protection d. short-circuit protection | show 🗑
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| 20.Overcurrent protection is required in each ungrounded conductor supplying a capacitor. The conductor ampacity shall not be less than ? of the rated current of the capacitor. a. 100% b. 125% c. 135%Correct d. 150% | show 🗑
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| show | 125%
The correct answer is: 430.24
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